User interface devices have been widespread, which enable a user's input motion or operation by manipulating a display screen with the user's finger, stylus, etc. Notably, in recent years, an increasing number of mobile information devices typified by such as smart phones, tablet computers, electronic books or PDAs (Personal Digital Assistants) have incorporated touch panels serving as a user interface device that receives the user's finger motion as an input signal.
Irrespective of whether a touch panel is incorporated or not, a mobile information device needs to be downsized for a greater mobility. Due to this, in case a mobile information device is equipped with a user interface device in the form of a plurality of physical input keys or buttons, these keys themselves need to be reduced in size, resulting in a risk that the operability of the mobile information device becomes poorer. In contrast, in case a mobile information device is equipped with a user interface device in the form of a touch panel using a plurality of virtual buttons instead of physical buttons, these virtual buttons can be well adjusted in size depending on functions assigned to these buttons, with a greater capability of improving the operability or maneuverability of the mobile information device.
A touch-panel input is created by a pointing action in which a finger is touched to the touch panel and points a given location on the touch panel. For this pointing action to ensure that a desired operation or function is invoked with the aid of a computer connected to the touch panel, correct pointing of a given target region on a display screen is crucial.
To achieve this, correct finger-pointing of a target area is needed, even in an example case in which a correct pointing action is difficult to be created due to the target area being too small on a screen, because, for example, the finger is needed to point a location close to a region of a displayed image on the screen, which is close to edges of the screen, or the finger is needed to point a location on a fine pattern of the displayed image.
To deal with these needs, a technique of allowing a user to enter a cursor-designated coordinate point only using a finger is disclosed in, for example, Patent Document No. 1. This technique allows a user to move a finger-touch position on a screen in order to move a cursor figure which is located at a position opposite to the finger-touch position with respect to a stationary reference point, to thereby enter a cursor-designated coordinate point.
Further, a mobile information communication device has been also proposed, which has a track pad disposed on one of both faces of this device, opposite to the face on which a display unit is disposed (see Patent Document No. 2). This device allows a user to hold a housing of this device with the user's one hand, and allows the user to perform input actions by touching the track pad of this device with a finger of the same hand holding this device. It is said that this allows the user to manipulate this device with the one hand's finger to thereby designate a given target point.